Opposition strongholds in Brazzaville were closed Tuesday following a strike over the re-election of Congo's veteran ruler Denis Sassou Nguesso in polls his rivals say were marred by "massive fraud".

Sassou Nguesso was declared the winner of the March 20 election, extending his 32 years in power in a result which has been challenged by five defeated opposition candidates.

He got a first-round win with 60 percent of the vote, according to the disputed official result.

Southern districts of the Congolese capital were deserted on Tuesday, including Total, the city's biggest market where the array of goods ranges from electronic appliances to caterpillars -- a local delicacy.

But on the fringes of the market, hundreds of women vendors ringed the pavements selling vegetables, fruit and soap.

The strike call was issued by runner-up Guy-Brice Parfait Kolelas who received more than 15 percent of the votes, third-place candidate Jean-Marie Michel Mokoko who polled nearly 14 percent, and three others: Claudine Munari, Andre Okombi Salissa and Pascal Tsaty Mabiala.

They called for a repeat of the "ville morte" (dead city) national strikes which have taken place in recent months to protest Sassou Nguesso's controversial bid for a third term.

The oil- and timber-rich Republic of Congo has been on edge since an October constitutional referendum that ended a two-term limit on presidential mandates, allowing Sassou Nguesso, a 72-year-old former paratrooper colonel, to run again.

Critics accuse him of rampant corruption and nepotism, blasting the referendum result as a "constitutional coup".

'No choice'

But biting poverty in the country, where the oil riches only benefit a fraction of the population, has forced many of those demanding jobs and decent living conditions to work through the strike.

"Politics doesn't interest me. Politicians are all the same. If we don't come to work, how will be live?" said an onion seller, identifying herself as Maggie.

In the poor southern areas of Bacongo, Makelekele and Kinsoundi, most of shops downed their shutters. Police and soldiers spread out across the districts where youths loitered in the streets.

But life was normal in the central Poto-Poto district and there was little security presence.

Many people had to work on Easter Monday -- a public holiday -- like Andre, a young porter loading heavy sacks of sand on to large tippers parked on the beach.

"We suffer but we don't have a choice," said the 23-year-old, who is paid three euros ($3.40) an hour for back-breaking labour.

Andre's colleague Glad described the work as "much more than difficult.

"There are jobs here but they are reserved for Mbochi (members of Sassou Ngeusso's ethnic group) and for the northerners," he said.

Sassou Nguesso served as president from 1979 to 1992 and returned to power in 1997 following a civil war. He won two successive terms in 2002 and 2009, but both elections were contested by opposition parties.

In dire straits

While Congo saw "robust growth" of five percent over five years through to 2014, with oil and timber providing its main revenues, the country remains in dire straits.

"(Congo) continues to suffer from high rates of poverty and inequality, large infrastructure gaps, and important development challenges," a report by the International Monetary Fund released in July 2015 said.

Unemployment hit 34 percent in 2013, according to the last available data, and stood at 60 percent for those aged between 15 and 24.

The IMF fears "domestic instability" without progress in the battle to eliminate poverty.

The European Union had refused to send election observers to monitor the polls, saying conditions had not been met for a transparent and democratic vote.

And on Saturday, the Socialist Party of French President Francois Hollande issued a statement saying the vote results were "not credible", denouncing a lack of transparency in the electoral process in the former French colony.